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Commit fea3c9a5 authored by Peter Zijlstra's avatar Peter Zijlstra Committed by Greg Kroah-Hartman
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KVM: x86: Make indirect calls in emulator speculation safe 



(cherry picked from commit 1a29b5b7f347a1a9230c1e0af5b37e3e571588ab)

Replace the indirect calls with CALL_NOSPEC.

Signed-off-by: default avatarPeter Zijlstra (Intel) <peterz@infradead.org>
Signed-off-by: default avatarThomas Gleixner <tglx@linutronix.de>
Reviewed-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Cc: Andrea Arcangeli <aarcange@redhat.com>
Cc: Andi Kleen <ak@linux.intel.com>
Cc: Ashok Raj <ashok.raj@intel.com>
Cc: Greg KH <gregkh@linuxfoundation.org>
Cc: Jun Nakajima <jun.nakajima@intel.com>
Cc: David Woodhouse <dwmw2@infradead.org>
Cc: Linus Torvalds <torvalds@linux-foundation.org>
Cc: rga@amazon.de
Cc: Dave Hansen <dave.hansen@intel.com>
Cc: Asit Mallick <asit.k.mallick@intel.com>
Cc: Andy Lutomirski <luto@kernel.org>
Cc: Josh Poimboeuf <jpoimboe@redhat.com>
Cc: Jason Baron <jbaron@akamai.com>
Cc: Paolo Bonzini <pbonzini@redhat.com>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Arjan Van De Ven <arjan.van.de.ven@intel.com>
Cc: Tim Chen <tim.c.chen@linux.intel.com>
Link: https://lkml.kernel.org/r/20180125095843.595615683@infradead.org


[dwmw2: Use ASM_CALL_CONSTRAINT like upstream, now we have it]
Signed-off-by: default avatarDavid Woodhouse <dwmw@amazon.co.uk>
Signed-off-by: default avatarGreg Kroah-Hartman <gregkh@linuxfoundation.org>
parent 734e687d

arch/x86/kvm/emulate.c

+5 −5
Original line number Diff line number Diff line
@@ -25,6 +25,7 @@ 
#include <asm/kvm_emulate.h>

#include <linux/stringify.h>

#include <asm/debugreg.h>

#include <asm/nospec-branch.h>



#include "x86.h"

#include "tss.h"
@@ -1012,8 +1013,8 @@ static __always_inline u8 test_cc(unsigned int condition, unsigned long flags) 
	void (*fop)(void) = (void *)em_setcc + 4 * (condition & 0xf);



	flags = (flags & EFLAGS_MASK) | X86_EFLAGS_IF;

	asm("push %[flags]; popf; call *%[fastop]"

	    : "=a"(rc) : [fastop]"r"(fop), [flags]"r"(flags));

	asm("push %[flags]; popf; " CALL_NOSPEC

	    : "=a"(rc) : [thunk_target]"r"(fop), [flags]"r"(flags));

	return rc;

}
@@ -5306,15 +5307,14 @@ static void fetch_possible_mmx_operand(struct x86_emulate_ctxt *ctxt, 


static int fastop(struct x86_emulate_ctxt *ctxt, void (*fop)(struct fastop *))

{

	register void *__sp asm(_ASM_SP);

	ulong flags = (ctxt->eflags & EFLAGS_MASK) | X86_EFLAGS_IF;



	if (!(ctxt->d & ByteOp))

		fop += __ffs(ctxt->dst.bytes) * FASTOP_SIZE;



	asm("push %[flags]; popf; call *%[fastop]; pushf; pop %[flags]\n"

	asm("push %[flags]; popf; " CALL_NOSPEC " ; pushf; pop %[flags]\n"

	    : "+a"(ctxt->dst.val), "+d"(ctxt->src.val), [flags]"+D"(flags),

	      [fastop]"+S"(fop), "+r"(__sp)

	      [thunk_target]"+S"(fop), ASM_CALL_CONSTRAINT

	    : "c"(ctxt->src2.val));



	ctxt->eflags = (ctxt->eflags & ~EFLAGS_MASK) | (flags & EFLAGS_MASK);